The present technology relates to an engine component and a method of manufacturing the engine component by fracture separation. In particular, the present technology relates to the manufacturing of fracture separated connection rods (crack connecting rod).
From U.S. Pat. No. 3,994,054 A, it is known that in a crack connecting rod, at least one borehole is to be provided. The borehole extends parallel to the bearing eye and the fracture surface extends in the longitudinal direction of the borehole.
EP 1382866 B1 (U.S. Pat. No. 6,961,997 B2) discloses a method for the manufacturing of crack connecting rods in which the bearing eye of the crankshaft is hardened by case-hardening and then fracture-separated, whereby a defined hardening depth in the material and thereby a defined fracture pattern is achieved by suitable dimensioning and process parameters.
EP 1955799 B1 also discloses a method for the manufacturing of crack connecting rods in which the bearing eye of the crankshaft is hardened by case-hardening and is subsequently fracture-separated, whereby a defined hardening depth in the material and thereby a defined fracture pattern is reached by suitable dimensioning and process parameters.
It has been found to be disadvantageous that the steel connecting rods that are case-hardened by carburization and used in engines with a high power density, such as high-performance two-stroke engines in particular, are not able to satisfy the thermal requirements because when the steel that is case-hardened by carburization is exposed to an excessively high temperature, the surface hardness of the steel drops.
DE 102014117874 A1 proposes nitriding as an alternative treatment to carburization for case-hardening of the connecting rod, although it is not defined what the technically vague concept of “nitriding” refers to. DE 102014117874 A1 does not clearly indicate to what the term “nitriding” refers, since according to DE 102014117874 A1, martensite is to be formed by the “nitriding” in the same way as when the steel is subjected to carburization. Since according to DE 102014117874 A1 “nitriding” brings about a structural transformation, i.e. the formation of martensite, it can be excluded that the term “nitriding” that is used in this document refers to the nitriding treatment within the meaning of the present technology, that is where nitriding precipitation hardening occurs and where no martensite is formed such as in transformation hardening, occurring for example during carburization.
However, it is known that due to the different behaviour of steel that can be case-hardened by nitriding, fracture separation cannot be carried out in a similar manner as for steel that has been case-hardened by carburization. In particular, it is known that steel that can be case-hardened by nitriding does not exhibit brittle fracture behaviour in areas of its cross-sectional surface that are not reached by the nitriding case-hardening of the surface. Due to the plastic deformation of the material, the two fracture surfaces can no longer be assembled, or assembled with sufficient accuracy. No solution to this problem is disclosed in DE 102014117874 A1.
There is therefore a desire to provide fracture-separated engine components, in particular fracture-separated connecting rods, that have greater resistance to high temperatures, or to render practicable the fracture separation of engine components, in particular connecting rods, that have been case-hardened by nitriding.